1. Technical Field
The present disclosure relates to a semiconductor structure and the fabrication method thereof in particular, to trench power metal oxide semiconductor field effect transistor (MOSFET) and fabrication method thereof.
2. Description of Related Art
In order to fulfill energy saving and power consumption reduction requirements, power semiconductor devices e.g., power MOSFETs have been widely utilized in high voltage equipment. In the field of power semiconductor, the voltages withstanding capability (e.g., breakdown voltage BVdss) and conductivity characteristics (on resistance Ron) are known to be the most important capability indices for the power semiconductors.
In practice, to increase the breakdown voltage of a power semiconductor, at least a guard ring structure consisting of a p-n junction formed of a P-type semiconductor and an N-type semiconductor and a metal formed field plate is disposed on the wafer surrounding the power semiconductor. Taking a trench power MOSFET as an example, the guard ring structure may be formed by implanting a p-type dopant into the epitaxial layer having N-type dopant, then depositing metal layer thereon. Such that an electric field with moderate electric field distribution can be formed at the bottom (i.e. drain terminal) of the trench power MOSFET thereby increase the breakdown voltage of the trench power MOSFET. However, since each guard ring may only increase the breakdown voltage of the power semiconductor by a certain voltage value (e.g., 30V), thus most often a plurality of the above described guard ring structures must be disposed accordingly for the power semiconductor to attain the required breakdown voltage. Implementing the described guard ring structure not only may waste the usable wafer area but also increase the manufacturing complexity henceforth the manufacture cost of the power semiconductor may be substantially increased and thereby reduce the associated economic efficiency.